Microwave tuning units



OCL 11,1965 s. MANFANovsKYQ 3,278,869

MI GROWAVE TUNING UNITS 75 74 73 16 P' 11 fz INVENTOR |1J ATTORNEY Oct- 11, 1966 s. MANFANOVSKY 3,278,869

MICROWAVE TUNING UNITS 2 Sheets-Sheet 2 Filed Feb. l5, 1965 xNvEN-ron lf2-R65 ANPA/vaak,

ATTORNEY United States Patent O 3,278,869 MICROWAVE TUNING UNITS Serge Manfanovsky, Wayland, Mass., assigner to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Feb. 15, 1965, Ser. No. 432,481 16 Claims. (Cl. 333-83) This invention relates to microwave tuning units, and more particularly to such units that are eflicient and selective in the high microwave frequency range, as above ten kilomegacycles.

The tuning unit of the present invention utilizes a wave guide body in which a piston is axially movable. The input signal is introduced centrally of the body through a small opening or iris; and the output signal passed in like manner. The piston is formed as a low-pass filter, enhancing the selectivity and gain of the tuner to the desired frequencies. A novel array of llongitudinal ridges projects -along the wave guide body which stabilizes and maintains the signal polarization therealong. The selected signal is maintained therein without power loss, and results in a wider band of tuning by the tuner unit hereof. The invention tuners are effective over a 1:1.5 band, in the over kmc. range, as compared to 1:1.2 of prior tuners.

In a preferred form of this invention, two tuning cylinders are juxtaposed, with their pistons in common drive and the two cylinders signal coupled by Ia common iris at their boundary. The two tuning elements are thus in series, and results in a clean selective output at the desired .tuned-in signal frequency, of enhanced magnitude. Standing waves occur at the interior resonant piston setting, one-half wave-length from the opposite end of the cylinders. The ridge sets in each cylinder are arrayed perpendicularly to a line along which the coupling openings or irises `are arranged. These ridges hereof prevent twisting of the signal field along the tuner, and serve as a mode filter. The pistons are slotted to ride firmly along the ridges as tracks.

The above and further features, advantages and objects vof this invention will become apparent from the following description of .an exemplary embodiment thereof, illustrated in the drawings, in which:

FIGS. l and 2 are respective plan and elevational views of the exemplary microwave preselector.

FIG. 3 is a diagrammatic representation of the invention tuner.

FIG. 4 is an enlarged perspective illustration of a piston of the exemplary tuner.

FIGS. 5 and 6 are respective plan and elevational views of the body portion per se of the preselector, partially broken away.

FIG. 7 is an end view of the body portion of FIGS. 5 and 6.

The exemplary microwave preselector has a central body 16, .the cavity assembly, of outwardly rectangular form. The contained two pistons 17, 18 are longitudinally settable through associated spring-biased rods 20, 21. A cross-link 22 connects the outer ends of rods 20, 21 to move them in unison. Helical springs 23, 24 surround the respective pist-on rods 20, 21. A retainer 25 on link 22 4secures 4the end of spring 24; retainer 26, of spring 23. Link 22 also secures the front ends of two transverse guide-rods 27, 28. A rear link 29 secures the back ends of the rods 27, 28. Springs 30, 31 are set about the guide rods 27, 28. The forward ends 32, 33 of the springs 30, 31 connect with front bracket 34. The guide rods 27, 28 pass through respective bushings 3S, 36 in bracket 34.

A center bracket 37 is secured lto the left end of the tuner body 16; rear bracket 38, to its right end. Rods ICC 37, 38. Rods 27 passes through a bushing 41 in "rear Y` bracket 38. Guide rods 27, 28 are coupled to an external control arm lor rod (not shown) at sleeve 42 that extends.

from front link 22. The axial relation of the sleeve 42\v and link 22 is adjustable through screw 43. The piston `\AV rods 20, 21 are individually adjustable, for tuning balance, through their respective -adjustment screws 44, 45; and held preset by spring locks 46. The springs 23, 24 and 30, 31 hold the Ipistons 17, 18 in their adjustment and precise settings, in `stable position.

The pistons 17, 18 are axially positioned in their respective cavities within central body 16, see FIG. 3. The exemplary `cavities 47, 48 are cylindrical wave guides in form; rectangular ones may instead be used. The input microwave signal is impressed at coupling 50, and passes into cavity 47 through a coupling opening or input iris 51. The preselector tuned output is passed externally of cavity 48 through an output iris 52, into a crystal mixer 53. The mixer 53 has two coaxial cable terminals 54, 55 for heterodyning of the signal output of the preselector 16. The cavities 47, 48 are signal connected through a common coupling iris 56 in their boundary web 59 (FIG. 7).

The tuning or selection of a desired signal, at frequency fo, is accomplished by setting of the pistons 17, 18 at the distance from the cavity ends 57, 58 equal to one-half of the wavelength of the frequency fo. Such distance is from the inner faces 60, 61 of the pistons 17, 18 to the respective inner surfaces of the reflector ends 57, 58. Such resonance -cavity length at half-wave Ilength emphasizes the signals at the corresponding frequency fo, and attenuates the passage of other signals that may be injected at input 50, therewith. The dual preselection tuning in the coupled cavities 47, 48 results in excellent preselection and emphasis of the tuner-in signal fo and rejection of the unwanted signals, affording selective tuning.

The invention tuner is elicient and effective for frequencies above about 10 kmc., and accommodates a particularly wide band in the ratio of 1:1.5 in such frequency range. Towards this end, each signal cavity 47, 48 is provided with a set `of longitudinal ridges-63, 64 and 65, 66. The ridges are arrayed 180 apart and centrally in their respective wave-guide cavities 47, 48, in planes perpendicular to the alignment of the irises 51, 52, 56 (FIG. 7). Such arrangement of the ridges places them basically perpendicular to the electric field E of the signals in their wave-guide cavities 47, 48. The ridges 63, 64 and 65, 66 project into the cavities, being mounted from the cavity Walls. They are smooth, highly polished conductive surfaces, as are the other interior cavity and piston areas.

The ridges 63, 64 and 65, 66 serve to maintain the signal polarization within the wave-guide cavities 47, 48 as original projected or set by their iris inputs. This important feature stabilizes the tuning system at the high frequencies thereof, and prevents the upsetting or twisting of the electromagnetic waves along the cavities that would result in loss of signal energy. The stabilizing ridges result in efficient selectivity and better gain ratio over a wider signal band than heretofore accomplished with over 10 kmc. signals. Further, the ridges 63, 64 and 65, 66 also serve as a mode filter at the selected frequency fu, significantly attenuating the TM modes. The TEM mode is not interfered with, and progresses very well through the system, for the extended band of the tuner hereof.

The exemplary pistons 17, 18, illustrated in FIGS. 3 and 4, contain three spaced disc portions 70, 71, 72 and 73, 74, 75 respectively. Their dimensions and spacing are proportioned to serve as very low-pass filters to the tuning band. For a l0 to 15 kmc. band pres-elector, these disc I is 6.063" long, 1.675 high, and 1.0 wide. 4""drical cavities 47, 48 have 0.750" internal diameters to accommodate the sheathed pistons. The ridges 63, 64

3 diameters are 0.7l70; 0.249" wide; and spaced apart 'by 0.389". Such piston construction serves to shortcircuit or pass extraneous signal frequencies to ground,

' behind their inner faces 60, 61, while maintaining the "zz standing-wave resonance half-wavelength actlon across the remaining open regions of cavities 47, 48. The piston discs 70, -71-, 72 and 73, 74, 75 each are slotted at a and b to ride on their respective ridge sets 63, 64 and 65, 66.

The slots a, b, are made to smoothly and closely conform with the ridge projections, the latter serving as rails to further stabilize the movement and precision settlng f of the pistons.

It is desirable to surround the pistons 17, 18- with sheets of durable, low-loss, self-lubricating material as Teflonf This establishes non-metallic friction for accurate low frictional displacement of the pistons, without contact noise, and without interfering with the choking-off to ground of the unwanted frequencies.

'The closely-sheeted pistons are fitted in close sli-dable contact relationship with the inner cylindrical faces of cavities 47, 48.

The exemplary central body 16, for the indicated band,

The cylinand 65, 66 each project into the cavities by 0.069 (-|-.002, .001). The linear ridges extend across the operating positions of the pistons; being 3.622" long, ending about 1.425 from faces 57, 58. The coupling iris 56 is formed in the central web 59 common to both cavities 47, 48. The web thickness is 0.025. Iris 56 is oval in shape, 0.176 by 0.113. `Coupling plates 77, 78 are 'brazed or s'ilver soldered into cut-outs in lbody 16, on opposite sides 4of iris 56. vThe respective irises 51, l52 are larger than and somewhat offset with respect to i-ris 56.

While the present invention has lbeen described in connection with the exemplary embodiment, it is to be understood that modifications, variations and changes may be made therein without departing from the broader principles and scope of the invention as set forth inthe appended claims.

What is claimed is:

1. A preselector for microwave signals comprising a body containing a longitudinal cavity, a set of ridges extending into the cavity from substantially opposite sides Y thereof, and a piston operable in the cavity for the selective tuning thereof, whereby the ridge sections-in the effective cavity portion stabilize the electromagnetic polarization of the tuned signals therein.

'2.-A microwave preselector as claimed in claim 1, in which said cavity is of cylindrical form.

3. A microwave preselector as claimed in claim 1, in which said piston contains slotted portions that ride on said ridges in stable array.

4. A preselector for microwave signals comprising a l body containing a longitudinal cavity, a set of ridges eX- tending into the cavity from substantially opposite sides and longitudinally thereof, and a piston operable in the cavity for the selective tuning thereof With respect to a reflection wall therein, whereby the ridge sections in the effective cavity portion stabilize the electromagnetic polarization of the tuned signals therein.

5. A microwave preselectoras claimed in claim 4, in

which said cavity is of cylindrical wave-guide configuration, an input and output aperture in the walls of the 6o respective cavities each opposite a side of said iris and in substantial alignment.

6. A microwave preselector as claimed in claim 5, in which the planes of said ridge sets are substantially perpendicular to said alignment.

7. A microwave preselector as claimed in claim 6, in which said piston contains slotted portions that ride on said ridges in stable array.

8. A microwave preselector as claimed in claim 4, in which said piston contains slotted portions that ride on said ridges in stable array and being formed as a plurality of spaced conductive discs effective as a -loW pass filter to untuned signals.

9. A preselector for microwave signalscomprising. a body containing/a first and second longitudinal cavity adjacent to each other in which an aperture electromagnetically couples said cavities,`a first and second set of ridges extending into the respective cavities from substantially opposite sides thereof, and a first and second piston operable in the respective cavities for the selective tuning thereof, whereby the ridge sections in the effective cavityV portions stabilize the electromagnetic polarization of the tuned signals therein. l

10. A microwave preselector as claimed in claim 9, in

which said cavities are of cylindrical wave-guide configuration.

11. A microwave preselector as claimed in claim 9, in which each said piston contains slotted portions that ride on said ridges in stable array.

12. A preselector for microwave signals comprising a body containing a first and second longitudinal cavity closely adjacent to each other with a thin web therebe-v tween in which an iris electromagnetically couples said cavities, a firstand second set of ridges extending into the respective cavities from substantially opposite sides and longitudinally thereof, and a first and second piston operable in the respective cavities for the selective tuning thereof with respect to reflection walls therein, whereby the ridge sections in the effective cavity portions stabilize `the electromagnetic polarization ofthe tuned signals therein.

13. A microwave preselector as claimed in claim 12, in which said cavity is of cylindrical wave-guide configuration, an input and output aperture in the walls of the respective cavities each opposite a side ofl said iris and in substantial alignment. j

14. A microwave preselector as claimed in claim 13, in which the planes of said ridge sets are substantially perpendicular to said alignment.

15. A microwave preselector as claimed in claim 14, in which` each said piston contains slotted portions that ride on said ridges in stable array and being formed as a pluralityvof spaced conductive discs effective as a low pass lter to untuned signals.

16. A microwave preselector las claimed in claim 12, in which each sai-d piston contains slotted portions that ride on said ridges in stable array and being formed as a plurality of spaced.l conductive discs effective as a low pass filter to untun-ed signals.

References Cited by the Examiner UNITED lSTATES PATENTS 2,831,171v 4/1958 Brown 333--83 HERMAN KARL SAALBACH, Primm-y Examiner.

L. ALLAHUT, Assistant Examiner. 

1. A PRESELECTOR FOR MICROWAVE SIGNALS COMPRISING A BODY CONTAINING A LONGITUDINAL CAVITY A SET RIDGES EXTENDING INTO THE CAVITY FROM SUBSTANTIALLY OPPOSITE SIDES THEREEOF, AND A PISTON OPERABLE IN THE CAVITY FOR THE SELECTIVE TUNING THEREOF, WHEREBY THE RIDGES SECTIONS IN THE EFFECTIVE CAVITY PORTION STABILIZE THE ELECTROMAGNETIC POLARIZATION OF THE TUNED SIGNALS THEREIN. 